Polyvinyl fluoride film having a layer of photosensitive emulsion thereon



United States Patent O Int. Cl. G03c 1/78 US. Cl. 96-87 1 Claim ABSTRACT OF THE DISCLOSURE An image-receptive, flame-treated polyvinyl fluoride film having 5% to 25%, preferably 15% to 23%, of pigment such as carbon black and 2% to 6% of particulate material such as silica and having an optical density of at least 8.0 and a stiffness of about 100 mg. per inch.

The present invention relates to photography and more particularly, is directed to improvements in and relating to a polyvinyl fluoride film structure incorporated into a photosensitive element utilized in camera structures, and the process of manufacture therefor.

The principal object of the present invention is to provide an image receptive element comprising a polyvinyl fluoride film structure having an image receptive material adhered thereto for receiving a photographic transfer image.

As is understood in the art, a photographic transfer process may be carried out to form a reverse image in an image receptive material of a latent image contained in an exposed photosensitive element. By one practice, a transfer image may be effected by spreading a viscous, aqueous alkaline solution of a silver halide developer and a silver halide solvent between and in contact with an image receiving material and an exposed silver halide photosensitive material which are arranged in superposed relation. An image-wise distribution of the image forming components is provided as the result of the development of the latent image in the photosensitive layer. The image forming components are transferred in solution, without appreciably disturbing the image-wise distribution, from the photosensitive layer to the image receiving material to provide the desired reverse image. In one embodiment, the viscous processing liquid is spread in a liquid film between a photosensitive element comprised of a silver halide emulsion and a print or image receiving element comprising, preferably, a suitable silver precipitating layer. The processing composition effects development of the latent image in the emulsion and substantially contemporaneously therewith forms a soluble silver complex, for example, a thiosulfate or thiocyanate, with undeveloped silver halide. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated inthe silver precipitating layer of said element to form therein a positive image in silver.

The above-described process is ordinarily carried out in a self-developing camera apparatus which is provided with means for advancing an exposed film containing a latent image in a photosensitive layer and image-receptive elements or materials through a plurality of predetermined positions therewithin and means for separating said elements after exposure. In such apparatus, the elements are maintained under appreciable tension and it is, therefore, necessary to insure that such elements, particularly the image-receptive elements do not become severed within the camera so as to cause failure of the intended camera operation.

Heretofore, the image-receptive element has comprised 3,497,357 Patented Feb. 24, 1970 a paper base or a base of cellulose triacetate, but one of the major problems associated with such bases is the inability to withstand cycling at higher temperature and higher humidity conditions for extended periods of time. Thus, such image receiving sheets when held in contact in superposed relation with the exposed film within a camera structure are easily apt to exhibit severe buckling or unevenness of the respective image receiving sheets which, of course, is highly undesirable. Also, the superposed positioning of the image receptive elements in a camera structure necessitates special anti-blocking characteristic between the base sheet and the image receptive material such that the image receptive material on one sheet is not damaged or disturbed when in contact with the back of the image receiving sheet of a next adjacent superposed element.

According to the present invention there is provided an image receptive sheet of a polyvinyl fluoride film comprising 5% to 25%, preferably 15% to 23%, by weight, based upon the total weight of said polyvinyl fluoride film, of opacifying pigment and 2% to 6%, by weight, based upon the total weight of said polyvinyl fluoride film, of an inert inorganic particulate material having essentially uniform average particle diameter within the range of 2 to 20 microns and a refractive index of about that of polyvinyl fluoride, said polyvinyl fluoride having an optical density of at least 8.0 throughout the photosensitive spectrum and a stiffness of about mg. per inch, said film having an image receptive material on one surface thereof.

According to the present invention there is further provided a process for treating the surface of the abovedescribed polyvinyl fluoride film to render the surface thereof adherent to other materials, without adversely affecting the blocking characteristics thereof, which comprises bringing a surface of said polyvinyl fluoride film continuously into intimate contact with a moving, relatively highly thermally conductive surface maintained at about 25 C. or less, passing said film while in contact with said surface through the stable, self-sustaining flame of a burner disposed parallel to said film and transversely of the direction of travel of the film, said burner being supplied with a gaseous fuel consisting essentially of hydrocarbon fuel, oxygen and nitrogen, said fuel being selected from the group consisting of paraflinic and olefinic hydrocarbons, the fuel equivalence ratio of said gaseous fuel being from 0.78 to 1.2, preferably 0.78 to 0.85, the oxygen ratio of said gaseous fuel being from 0.21 to 0.35 preferably 0.21 to 0.28, and the distance from the surface of the film to the discharge opening of said burner being not less than the distance below which the velocity of the burning gases escaping from the immediate vicinity of said discharge opening exceeds the burning velocity of the flame.

The nature and advantages of the present invention will be more clearly understood by the following description and the examples presented thereafter.

The polyvinyl fluoride film base suitable for the image receptive element of the present invention may be obtained from a monomer prepared by any one of the processes described in US. Patents 2,118,901; 2,480,560; 2,599,631; and 2,674,632. The preparation of the orientable polyvinyl fluoride may be according to the disclosure in US. Patents 2,419,008; 2,419,010; 2,510,783; 2,599,300; and 2,599,299. A preferred latent solvent containing polyvinyl fluoride film may be made in accordance with the process described in US. Patent 2,953,818 and oriented with solvent removal in accordance with the process described in US. Patent 3,139,470. The disclosure of the above mentioned patents is hereby incorporated by reference herein.

The suitable polyvinyl fluoride film for the image receptive element of the present invention contains from about 5% to 25% by weight, based upon the total weight of the film, of carbon black pigment, preferably about to 2.3% by weight, and from about 2% to 6% by weight, based upon the total weight of the film, of inert inorganic particulate material having essentially uniform average particle diameter within the range of 2 to microns and a refractive index approximately that of polyvinyl fluoride, the polyvinyl fluoride film having an optical density of at least 8.0 throughout the photosensitive spectrum.

The primary requirements of the inert, inorganic particulate material anti-blocking agent contained in the film may be achieved by the use of silica particles such as, for example commercially available products known as Syloid 244 and Syloid 72, products of the Davison Chemical Division of W. R. Grace & Company.

Carbon black incorporated in the film within the range above specified will result in a film having the required optical density.

Furthermore, the polyvinyl fluoride film for the image receiving element should have a stiffness of at least 100 milligrams per inch and the film must be characterized by improved blocking characteristics such that the imagereceiving emulsion coating placed on the treated surface thereof will not exhibit critical blocking when exposed to high relative humidity at a high temperature as will be exemplified further in the examples herein.

The film base, while meeting the blocking requirements, also must be characterized by improved adhesion characteristics, i.e., the film base must have adequate adhesion to emulsion (gelatin) coatings and adhesion to paper leaders used for advancing the film structure in camera structures as will be exemplified further in the examples herein.

The image receiving material may comprise a single layer or multiple layers of any image-receptive material. Image-receptive material may also contain various photographic agents or reagents, such as for example, one of the vigorous silver precipitating environments described in US. Patents 2,698,237 and 2,698,245. A wide choice of materials are suitable for this use. However, heretofore, many of these materials have not been satisfactory in combination with a paper base as regards stiffness, adhesion, blocking, opacity, and/or buckling (dimensional stability) characteristics.

In order that the film base will have the requisite adhesion for both the image-receiving material thereon and the adhesively heat sealable paper leaders attached thereto, the polyvinyl fluoride film is treated by a flame in the following manner. The film is subjected to flame treatment by bringing the respective surfaces in sequence continuously into contact with a moving relatively highly thermally conductive surface maintained at approximately C. or less, passing the film while in contact with the surface through the stable, self-sustaining flame of a burner disposed parallel to the film and transversely of the direction of travel of the film, the burner being supplied with a gaseous fuel consisting essentially of hydrocarbon fuel, oxygen and nitrogen, the fuel being selected from the group consisting of paraflinic and olefinic hydrocarbons, the fuel equivalence ratio of the gaseous fuel being from 0.78 to 1.2, the oxygen ratio of the gaseous fuel being from 0.21 to 0.35, and the distance from the surface of the film to the discharge opening of the burner being not less than the distance below which the velocity of the burning gases escaping from the immediate vicinity of the dis- 1 charge opening exceeds the burning velocity of the flame.

In a typical embodiment, the image-receiving element of the invention comprises an image-receiving material (a) which preferably contains silver precipitating nuclei that is disposed on a support layer ([2) of the above-described polyvinyl fluoride film. The image-receiving element is usually disposed in a camera and is brought into contact with a photosensitive element comprising preferably a photosensitive silver halide gelatin emulsion layer (0) disposed on a suitable support (e) which may be of the above-described polyvinyl fluoride film. In use, a processing or developing composition is distributed to provide a substantially uniform layer (d) between the image-receiving material (a) and the photosensitive emulsion layer (0) in accordance with the procedures disclosed in US. Patent 2,543,181. For example, one or more rupturable containers may be attached to either photosensitive emulsion layer (0) or image-receiving layer (a) such that upon superposition of the respective layers (0) and (a) said container or containers are so positioned as to be capable, upon rupture, of releasing their contents in a substantially uniform layer between and in contact with an opposed surface of each of said layers. Rupture of the container or containers and spreading the contents thereof may be accomplished, for example, by compression between a pair of opposed, suitably spaced rollers.

In use, the photosensitive silver halide emulsion (c) is exposed to a predetermined subject matter to form therein a latent image of said subject matter. The exposed emulsion is superposed on the image-receiving element (a) and the photographic processing composition (d) is spread between the opposed surfaces of said photosensitive emulsion (c) and said image-receiving element (a). Reagents permeate into the photosensitive emulsion (0), developing the latent image contained therein and forming a soluble silver complex from the unexposed silver halide. Soluble silver complex in solution in the reagent is trans ported from photosensitive emulsion layer (c), at least in part, by imbibition, toward print-receiving stratum (a) wherein the complex is reduced to silver to provide the desired reversed, positive image. The lamination formed by the spreading of processing composition layer (d) between photosensitive emulsion (c) and print-receiving element (a) is kept intact for approximately /2 to 1 /2 minutes, preferably 1 minute, and at the termination of this time interval print-receiving layer (a) is dissociated from emulsion (c), as for example, by stripping. The processing composition or layer (d) remains substantially bonded to the photosensitive emulsion layer (0) when print-receiving layer (a) is stripped from photosensitive emulsion (c) thereby preventing the adherence of residual processing composition to the print-receiving layer (a), which might result in possible stain formation and image degradation due in part to the constituent components thereof.

The principle and practice of the present invention will now be illustrated by the following examples which are provided to show and exemplify the use and nature thereof, but it is not intended that the invention be limited thereto since modifications in technique and operation will be apparent to anyone skilled in the art.

EXAMPLE 1 A blend tank was charged with a mixture of 36% solids in N,N-dimethylacetamide, wherein the solid represented on a dry weight basis 80.75% polyvinyl fluoride, 18% lamp carbon black, 1% glycidyl polyether (Epon 1004), 0.25% triphenyl phosphite. This mixture was continuously pumped to a heated extruder connected to a slotted casting hopper having a 27 inch casting slot with an average lip spacing of 38 mils, from which issued at about C., a sample of coalesced latent solvent-containing polyvinyl fluoride film which was immediately quenched by conducting the film through a water bath maintained at about 15 C. The casting draw-down was adjusted so that the quenched film averaged about 35 mils in thickness. The latent solvent containing film was then continuously stretched first longitudinally of its direction of extrusion 1.6 at 60 C. and then transversely of its direction of extrusion 2.2x at C. followed by exposure for about 30 seconds to an ambient temperature in the range of C. to C. to volatilize the remaining N,N'-dimethylacetamide. The resulting 3.8 mils thick, polyvinyl fluoride film exhibited an optical density of greater than 9 and a stiffness of 110 mg. per inch as measured by the standard test employing the Gurley Stiffness Tester. (W. & L. E. Gurley, Troy, New YorkModel No. 4171.)

Employing the blocking test described herein, the film exhibited no blocking.

Samples of the film were subjected to flame treatment by bringing the respective surfaces thereof in sequence continuously into contact with a moving relatively high thermally conductive metal roll maintained at approximately 25 C. and passing the film while in contact with the roll through the stable, self-sustaining flame of a burner disposed parallel to the film and transversely of the direction of travel of the film. The burner was supplied with a gaseous mixture consisting essentially of hydrocarbon fuel (Pyrofax brand propane natural gas derivative containing 96.5% propane, 2.5% ethane and 1.0% butanes), oxygen and nitrogen. The fuel equivalence ratio of the gaseous mixture was 0.8 and the oxygen ratio of the gaseous mixture was 0.278, and the distance from the surface of the film to the discharge opening of the burner was 3.0 millimeters, and the burner lip opening was 100 mils. The film speed past the flame was 275 feet per minute. Similarly, film was passed in like manner at varying distances from the burner opening to the surface of the film and the resulting adhesion and blocking test carried out, the results thereof are tabulated below.

Film to Adhesion Blocking burner (gm./in.) (percent distance (paper Adhesion area Sample (mm.) leader) (gelatin) Blocking removed) 3.0 *324 OK CBll 6.3 *258 OK. SB Hairlines 8.0 *234 OK- NB 0 95 Weak NB 0 *Papersplitting bond.

EXAMPLE 2 A polyvinyl fluoride film (dry weight basis 76.75% polyvinyl fluoride, 18% carbon black, 4% Syloid 72, 1% thermostabilizer-glycidyl polyether (Epon 1004), 0.25% triphenyl phosphite) was prepared in a manner identical to that described in Example 1. Similarly, the film was flame treated as in the manner of Example 1. The film, having an optical density greater than 9, when treated with the film to burner distance of 3.0 millimeters had an NB blocking rating and zero percent area removed a satisfactory adhesion for gelatin containing coatings to the film, an adhesion of 240 grams per inch papersplitting bond, and exhibited no tendency toward buckling.

By way of contrast, a control film of cellulose triacetate exhibited a blocking rate of CB 111 and 50% area removed.

BLOCKING TEST To rate on a relative basis the propensity of the back surface of film base materials (either untreated or after anti-blocking treatments) for blocking to the emulsion coated side.

Materials (a) For each test: 1 piece of control negative and 1 piece of test material to a size of 4% inches by 3% inches. (b) For each series of test: at least one control set consisting of 2 pieces of control negative cut to 4% inches by 3% inches.

Equipment For each test: one set of Type 108 film pack parts (Polaroid). For each series:

(a) A vacuum desiccator containing about a inch deep layer of saturated KNO solution plus some undissolved KNO in contact with both liquid and gas above liquid.

(b) A vacuum pump (either mechanical or water operated aspirator).

(c) A means of holding the evacuated desiccator at 100 :2 F.

Procedure Place plastic front of film pack face downward on table. Insert test material into this unit with the side to be evaluated facing upwards. Insert piece of control negative with emulsion side downward and thus in contact with the surface of the test material being evaluated. Center materials over opening taking care that edges of each line up. Insert pressure plate, and finally slide on spring back. Prepare at least one control pack containing 2 pieces of control negative in back-to-front relationship.

Stack film packs on support plate over the KNO solution in the desiccator leaving an air space between each. Cover desiccator and evacuate desiccator until the KNO solution just starts to boil. Close desiccator valve and place unit in the controlled temperature chamber for 16 hours. At the end of the test period, open desiccator, remove packs and allow to equilibrate to room conditions for 2 hours before opening the packs to evaluate degree of blocking.

Rating of results NBNo blocking, surfaces slide freely.

SBSlight blocking, surfaces do not slide freely but separate at a touch and show no marring.

CBICritical blocking, level I. Surfaces do not slide freely and when separated show slight evidence of blocking.

CBIIAs CBI but show substantial evidence of marring but no emulsion peeling.

CBIIIAs CBI but emulsion peels or base tears when separation is attempted.

The blocking characteristic is also evaluated by determining on a percent basis the area of surface emulsion that is removed under the above test conditions.

Adhesion tests The following is the adhesion test procedure for photographic base film for adherability of gelatin containing coatings.

Procedure: (1) Dissolve 0.5 gram of a suitable dye (wool yellow extra concentrateAllied Chem.National Aniline) in 20 milliliters of distilled water. (2) Swell 10 grams of air dry photographic grade gelatin in 20 milliliters of cold distilled water for 20 minutes. (3) Combine the dye with a gelatin, add 49.5 milliliters of the distilled Water and stir. The mixture is warmed to 40 C. in the Water bath until the gelatin is fully dissolved.

Cut a strip of test film base and control to about 2 by 6 inches. Dip the samples into the gelatin-dye solution and permit excess to drain off one corner. Allow the gelatin to set at room temperature. Place the strip into a 40 C. oven for one half hour and allow to dry.

After removal from the oven the samples are permitted to equilibrate at room temperature and humidity (72 F.45% R.H.). After equilibration the coating is cut lightly by drawing a razor blade across the surface. Transparent pressure sensitive cellophane tape is placed diagonally across the razor cut and pressed down firmly leaving only a tab on one end for pulling. Film base is held down firmly with one hand and the pressure sensitive tape is ripped up with a snap of the Wrist. Adhesion of the dyed gelatin to the tape is indicative of weak adhesive bonding between the gelatin and film base.

For determining the adhesion of a paper leader to the film base-a 1 inch wide paper leader coated with a nitrocellulose based adhesive /s inch wide is heat sealed to the film base at C. for A1, second dwell time at 40 pounds per square inch pressure. Using a Suter Tester, a peel test is conducted. Outstanding adhesion is noted when paper splitting occurs, prior to peeling.

What is claimed is:

1. A flame-treated polyvinyl fluoride film having 5% to 25%, by weight, based upon the total weight of said polyvinyl fluoride film, of carbon black and 2% to 6%,

by weight, based upon the total Weight of said polyvinyl fluoride film, of an inert inorganic particulate anti-blocking agent consisting of silica particles having essentially uniform average particle diameter within the range of 2 to 20 microns and a refractive index of about that of polyvinyl fluoride, said polyvinyl fluoride having an optical density of at least 8.0 throughout the photosensitive spectrum and a stillness of about 100 mg. per inch, said film having an image-receptive layer of photosensitive silver halide-gelatin emulsion on one surface thereof.

References Cited UNITED STATES PATENTS 2,322,037 6/ 1943 Lindquist. 3,139,470 6/1964 Prengle et al 264-289 3,240,604 3/1966 Cook 9687 X 8 Horne. Brennan et a]. l6l16 8 Hunter et a1. 9684 Bryan et :11. Bryan et al.

OTHER REFERENCES Tory, B. E.-Photolithography. 1953, Graphic Arts Monthly, Chicago, 111., TR 940, T 6. Only p. 191 made of record.

DAVID KLEIN, Primary Examiner U.S. Cl. X.R. 

